Buoyancy control system for deep diving submersibles

ABSTRACT

A buoyancy control system for a submersible having a hard ballast tank, a pump, an automatic spool positioning valve and a metering valve for transferring water ballast between the tank and ambient regardless of the direction in which the pressure gradient is working. The pump is only required to move water in one direction, which is against the pressure gradient, with the automatic spool positioning valve setting itself to control flow in the proper direction. Flow with the pressure gradient is controlled by a metering valve.

[451 June 6,1972

United States Patent Robbins, Jr.

....114/16 E Spear 14/16 E [54] BUOYANCY CONTROL SYSTEM FOR 3,204,596 9/1965 Fallon DEEP DIVING SUBWRSIBLES 821,895 5/1906 Roland w. Robbins, Jr., Arnold, Md.

Primary ExaminerTrygve M. Blix [72] Inventor:

[73] Assignee: The United States of America as Attorney-R. S. Sciascia, Q. E. Hodges and R, M. Wohlfarth represented by the Secretary of the Navy Oct. 26, 1970 ABSTRACT [22] Filed:

A buoyancy control system for a submersible having a hard [21] Appl. No.:

ballast tank, a pump, an automatic spool positioning valve and a metering valve for transferring water ballast between the [52] 1.1.8. E tank and ambient regardless fthe direction i which the pres- .B63g 8/00 114/16 R, 16 E, 125; 61/69 R sure gradient is working. The pump is only required to move [58] new of Search water in one direction, which is against the pressure gradient,

with the automatic spool positioning valve setting itself to con- References Cited trol flow in the proper direction. Flow with the pressure gradient is controlled by a metering valve.

UNITED STATES PATENTS 6 Claims, 5 Drawing Figures 803,175 Lake 14/16 E PATENTEnJun s 1972 SHEET 16F 3 PATENTEDJUH 5 1972 SHEET 20F 3 IN V EN TOR. ROL A ND W. ROBE/N5, Jr:

k mm mm m mm ow ATTORNEYS BACKGROUND OF THE INVENTION 1. Field of the Invention In the field of submersibles, especially small, deep-diving submersibles, there is a lack of a simple, reliable and efficient means for effecting a variable buoyancy capability. In large submersibles where space is not at a premium, extremely complex systems can achieve the desired reliability and efficiency.

The need for a buoyancy control system arises from the basic environmental reaction of the sea on a submersible. That is, as a submersible descends in the ocean, the hull and all external equipment and structures tend to compress thus increasing the density of the vehicle and making it less buoyant. Off-setting this is the added buoyancy created by the increased density of seawater as a function of depth. The two phenomena, however, do not usually exactly balance each other; hence, a means must be provided for artificially maintaining the vehicle in a neutrally buoyant state. This is essential in small submersibles since if the submersible is in other than a neutrally buoyant condition, it will continually drift either upward or downward. This would necessitate utilizing propulsive power to overcome this tendency should it be opposite to the desired direction of motion. The most readily available ballast is seawater, and therefore it is necessary only to pump the seawater in and out of appropriate tanks in the submersible to control buoyancy. Due to space and power limitations, the most efficient and effective means for varying the buoyancy of a small submersible is to pump water between a hard tank containing a gas ullage and the surrounding water of the environment.

2. Description of the Prior Art There have been numerous systems devised to provide a measure of buoyancy control for deep diving submersibles. Of those systems that have been adapted for use on small submersibles, there are two categories: discrete weights to be dropped and liquid transfer systems.

The discrete, expendable weight systems are perhaps the most primitive and least flexible. The weights could be drums of lead shot that are allowed to run out of the storage drum or somewhat larger weights releasably held to the exterior of the hull. The inflexibility of the system results from the method being irreversible, in that once ballast is dumped to increase buoyancy it cannot be retrieved to negate buoyancy. In order to regain a negative buoyancy a fluid transfer system is also needed in conjunction with the releasable weights.

The liquid transfer systems are more acceptable and have assumed many forms, among them a closed system containing a fluid of lesser density than the surrounding water, usually oil. The oil is pumped between a hard tank containing a gas ullage and a flexible bladder exposed directly to the seawater. This system besides being excessively heavy in air and of large volume has difficulty in maintaining the integrity of the closed transfer system. The most commonly used liquid transfer system is one utilizing a hard tank, four-way valve, and a pump. The system pumps seawater, through the four-way valve, either into or out of the hard tank. The undesirability of such a system stems from the state-of-the-art of four-way valves which are not tolerant of contaminated fluids such as seawater, and which leak when handling low viscosity fluids, such as seawater, under high pressure. There is also a metering problem as fluid is moved from a high pressure area to a low pressure area.

Thus the present buoyancy control systems by design, and as dictated by state-of-the-art components therein, are less than desirable.

SUMMARY OF THE INVENTION The present system utilizes any one of a series of seawater pumps that is connected to a hard tank, which has a gas ullage, through an automatic spool positioning valve. The gas ullage creates a predetermined pressure on the water in the hard tank and the pump either moves the water from the tank to ambient or from ambient to the tank against the pressure gradient. The highest pressure, whether it be the tank or ambient, sets the automatic valve for proper flow route. When it is desired to move the water from tank to ambient or ambient to tank with the pressure gradient, then the pump and automatic valve are bypassed and a metering valve meters the water from the higher pressure source to the lower. Thus, a simple ballast control system is established that utilizes seawater as the only liquid to be moved and eliminates the usual four-way valve with its inherent shortcomings. The automatic valve obviates the need to open or close a valve in the main pressurized stream, as the valve is set automatically by the pressure gradient to have the pump work thereagainst. Also, the metering valve eliminates the pressure gradient working with the direction of flow through the pump and four-way valve thereby eliminating a source of leakage.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view, in elevation, of the components of the system mounted in a pressure hull.

FIG. 2 is a sectional view of the automatic positioning valve where the ambient seawater pressure is higher than the tank pressure.

FIG. 3 is a sectional view of the automatic positioning valve of FIG. 2 where the pressure in the tank is higher than the ambient seawater.

FIG. 4 is a sectional view of the hydraulically operated metering valve in a closed position.

FIG. 5 is a sectional view of the metering valve of FIG. 4 in an open position.

DESCRIPTION OF THE INVENTION Referring now to FIG. 1 of the drawing, a pressure hull of a deep submersible 10 is shown with the ambient surrounding area 12 a deep seawater environment. A ballast control system 14, embodying the subject invention, can be mounted outside, or, as shown in the drawing within the hull 10. The system comprises a rigid ballast or hard tank 16 and a pump assembly 18 to move the seawater between the ambient 12 and the tank 16. A pair of valves, an automatic spool positioning valve 20 and a metering valve assembly 22 control the direction and path of the flow of the seawater.

The rigid ballast or hard tank 16, as mentioned above, is mounted within the pressure hull 10 of a submersible. The tank 16 has a reservoir or quantity of seawater 24 therein and a gas ullage 26, at pressure, to provide a predetermined pressure on the reservoir 24. The tank 16 is connected to the pump assembly 18 through a conduit 28 and the automatic spool positioning valve 20. A shut off valve 30 is mounted in the conduit 28 to provide a convenient means to seal off the tank 16 when it has been pressurized prior to a dive or when not in use.

The pump assembly 18 is made up of any conventional seawater pump 32, designed to pump under high ambient pressures, and a drive motor 34. The pump only pumps in one direction and is not required to have reverse flow characteristics. The inlet of the pump 32 is connected to the valve 20 by an inlet conduit 36, and the discharge of the pump is connected to the valve by a discharge conduit 38.

The automatic spool positioning valve 20, as shown in FIGS. 2 and 3, has an elongated cylindrical body 40 with a concentric bore 42 therethrough. A series of five bosses 44, 46, 48, 50 and 52 are provided on the exterior of the valve body 40 into which threaded ports 54, 56, 58, 60 and 62 are cut. An inlet spool 64 and a discharge spool 66 are mounted for movement within the bore 42 adjacent ports 56 and 60 which are connected by conduits 36 and 38to the inlet and discharge ports respectively, from the pump 32.

The inlet spool 64 has a center section 68 with a pair of poppets 70 and 72 formed on either end thereof. The poppets 70 and 72 have a spherical bearing face 74 and 76, respectively, with the circumference of the poppets permitting the spool to move along the bore 42. A series of notches, 78 and 80, in the circumference of the poppets 70 and 72, respectively, permit flow therethrough when the poppets are opened for flow. A valve seat assembly 82 is mounted concentric with the bore 42 and the center section 68 of the spool. The seat assembly 82 has a center tubular member 84 with a boss 86 and 88 at either end, respectively. A spherical ring seat 90 and 92 is cut into the bosses 86 and 88, respectively, so that when the associated poppet bears there against spherical faces 74 and 76 will seal therewith. Openings 94 are cut into tubular member 84 so that flow therethrough can reach the port 56. The seat assembly 82 is sealed to the bore 42 by any convenient means, such as rings 96, with the assembly being fixed against movement with the body 40 by any convenient manner such as snap rings 98.

The discharge spool 66 has a center section 100 with a poppet 102 and 104 on either end thereof. The poppets 102 and 104 have a spherical face 106 and 108, respectively, with the circumference of the poppets permitting the spool to move along the bore 42. A series of notches 110 and 112, in the circumference of the poppets 102 and 104, respectively, permit flow thereby when the spherical faces 106 and 108 are not seated. A valve seat assembly 114 and 1 16 is provided at each end of the discharge spool 66. The seat assembly 114 has a spherical ring seat 1 18 cut into the face thereof with an opening 120 therethrough so that when the poppet face 106 seals against the seat 118 the opening 120 is closed. The seat assembly 114 is sealed to the bore 42 in any convenient manner, such as an O-ring 122, with the assembly being fixed against movement by any convenient means, such as snap rings 124. The valve seat assembly 116 is the same as 114 but turned to accommodate the valve face 108. A spherical ring seat 126 is cut into the face thereof with an opening 128 therethrough. The seat assembly 116 is sealed to the bore with an O-ring 130 and fixed against relative movement by the snap rings 132. With the poppet valve assemblies mounted in the bore 42 a pair of threaded plugs 134 are secured in the ends thereof to complete the valve structure.

As mentioned above, the ports 56 and 60 are connected to the inlet and discharge of the pump 32, by conduits 36 and 38, respectively. The port 58 receives the conduit 28 thereby connecting the tank 16 to the valve 20. To complete the hookup of valve 20 into the system 14 a conduit 136 connects port 54 to the ambient water 12. This conduit brings ambient water into valve 20 when it is desired to pump water into tank 16. Also, a conduit 138 connects port 62 to the ambient water 12 when it is desired to pump water from tank 16 to the ambient 12.

In a deep diving submersible, with a hard tank 16 with its gas ullage 26, four possible conditions can occur: First, the ambient 12 pressure is greater than the pressure in the tank 16 and it is desired to transfer water from tank 16 to ambient 12; second, tank 16 pressure is greater than ambient 12 and it is desired to transfer water from ambient to the tank; third, ambient 12 is greater than tank 16 and it is desired to transfer water from ambient to the tank; and fourth, tank 16 pressure is greater than ambient 12 and it is desired to transfer water from the tank to ambient. The system as thus far disclosed is intended to deal with the first two conditions as is set forth hereinafter.

When it is desired to pump water from tank 16 to ambient 12 where the pressure in the tank is lower than ambient the spools 64 and 66 will be set automatically by the pressure gradient to permit such pumping as shown in FIG. 2. With port 54 connected to ambient l2 and port 58 connected to the tank 16,.the ambient pressure is greater and shifts spool 64 to the left thus sealing poppet face 74 against seat 90 and opening poppet face 76 to permit flow through notch 80, tubular member 84, openings 94, and through port 56 to the pump via conduit 36. Similarly, port 62 is connected to ambient, and the pressure there being greater than in port 58 which receives conduit 28 from tank 16, the spool 66 is moved to the right. This seals poppet face 106 against seat 118 and opens a flow path from the pump discharge conduit 38, around member 100, through notch 112 and opening 128 to conduit 138. Thus, for the conditions stated, the spools 64 and 66 are in proper position, and the greater the pressure difierential the greater will be the seal effected by the poppet valves. Therefore, the pump 32 need only be turned on to transfer water from tank 16 to ambient 12 against the pressure gradient.

In the second condition, when it is desired to pump water from ambient 12 to tank 16 when the pressure in the tank is greater than ambient the spools 64 and 66 will be set automatically by the pressure gradient to permit such pumping as shown in FIG. 3. As above, with ports 54 and 62 connected to ambient and port 58 connected to tank 16, via conduit 28, the pressure gradient acts on spools 64 and 66 to shift them into the proper position. Thus with the pressure in conduit 28 greater than ambient in conduits 136 and 138 the spool 64 is shifted to the right thus sealing poppet face 76 against seat 92 and opening a flow path from ambient conduit 136, past notch 78, through tubular member 84, openings 94 and into the pump inlet conduit 36. Similarly, the pressure in conduit 28 being greater than that in conduit 138, spool 66 shifts to the left thus sealing poppet face 108 against seat 126 and opening a flow path from pump discharge conduit 38 around member 100, through notch 110, and opening to the tank 16 through conduit 28. Thus again, for the conditions stated the pressure gradient has caused spools 64 and 66 to be automatically positioned so that the pump 32 need only be turned on to transfer water from ambient 12 to tank 16 against the pressure gradient.

In the third and fourth conditions mentioned above, when it is desired to transfer water with the pressure gradient it is necessary only to meter the water as a flow path is established from the high pressure source, whether tank 16 or ambient 12, to the low pressure sink, whether ambient 12 or tank 16.

The metering valve assembly22 provides a means to bypass the automatic spool positioning valve 20 and the pump assembly 18 in these conditions. The metering assembly 22 has a metering valve 140 which is connected to conduit 28 by a conduit 142 and connected to ambient 12 by conduit 144. The valve 140 is actuated by a hydraulic pump 146 connected to the valve by conduit circuit 148.

The metering valve 140 shown in FIGS. 4 and 5 is a representative type of valve for such an application. The valve has a main cylindrical body 150 with identical concentric bores 152 extending inwardly from each end thereof. At the inward end of the bores 152 a pair of smaller concentric counter bores 154 extend inwardly therefrom with the bottom of the bores 154 being connected by a counter bore 155 that is smaller than bore 154. The bottom of the bores 154 are the seats for valve springs 156 which hold poppets 158 in a closed position against valve seats 160, as shown in FIG. 4. The poppets 158 have a spherical face 162 that seats against spherical ring seats 164. The poppets have notches 166 out into the circumference thereof to permit flow therearound when they are unseated. The valve seats have openings 168 to permit flow therethrough when the poppets are not seated thereagainst. The valve seats 160 are sealed against the bores 152 by O rings 170 and retained in position by snap rings 172. A pair of ports 174 open through the cylindrical body 150 into the bores 152 to receive the conduits 142 and 144. With the valve 140 thus far assembled, end caps 176 are threaded into each end thereof to enclose the body thereof. The caps 176 have concentric bores 178 extending inwardly from the exterior end thereof. At the inward end of each bore 178 a counter bore 180 extends inwardly therefrom, with a second counter bore 182 extending through the end of the cap 176 into the bore 152. A piston assembly 184 has a piston head 186 with a diameter slightly less than that of bore 178 to permit reciprocation therein. The piston head 180 is sealed to the bore 178 by a pair of piston rings 188. The piston head 186 has an elongated piston rod 190 attached to one side thereof to extend through and reciprocate in the counter bore 182. A seal 192 is mounted in the cap 176 along the counter bore 182 to seal the rod 190 therewith. The bottom of counter bore 180 acts as the seat for return spring 194 whose other end bears against the piston head 186. A series of radial openings 196 open into the bore 180 to prevent a buildup of pressure that might blow by the seal 192 or rings 188 as the piston head 186 reciprocates. A snap ring 198 is mounted near the open end of bore 178 to limit the outward travel of the piston assembly. The conduit circuit 148 is threadedly received in the open end of the bores 178 to transmit the hydraulic activation pressure thereto.

The pump 146 which supplies the hydraulic activation pressure to the valve 140 is a simple and well known design with a pressure release mechanism 200. As the handle is manipulated, pressure builds up in the circuit 148 and drives the piston assemblies 184 inwardly in valve 140. This moves the piston rods 190 into contact with the poppets 158 and moves them off their seats 164 as shown on the right of FIG. 5. The inward movement of the piston assembly compresses springs 194 so that when release mechanism 200 is activated the piston assemblies will be driven outwardly allowing the poppets 158 to reseat on the valve seats 160. There is no need for equalization of pressure into the end caps to insure unseating of the poppets 158 as the pressure in either conduit 142, from tank 16, or conduit 144, from ambient 12, will unseat one of the poppets as shown on the left in FIG. 5. Thus, when pressure is built up in circuit 148 the piston assembly 184 will bottom against the open poppet and the pressure will then move the other piston assembly against the still closed poppet. In this valve, as in valve 20, the greater the pressure gradient the greater the seal between the poppet 158 and its ring seat 164 as the pressure forces the downstream poppet closed.

Thus, when it is desired to transfer water between ambient l2 and tank 16 with the pressure gradient, as set forth above as the third and fourth conditions, the metering valve assembly 22 can utilize the pressure gradient so that no pumping or other power consuming operations are needed.

In the third condition'when the pressure of ambient 12 is greater than tank 16 and it is desired to transfer water from ambient to the tank, the pump 146 is manipulated to pressurize circuit 148. As the ambient 12 is at a higher pressure than the tank 16, the poppet 158 adjacent the ambient conduit 144 will be unseated by the ambient pressure and the pressure in circuit 148 will drive the piston assembly 184 against the poppet adjacent the conduit 142 that leads to tank 16 through conduit 28. With both poppets open water will flow through conduit 144, valve 140, conduit 142, and conduit 28 into tank 16. When sufficient water has been transferred the pressure release 200 is activated and the springs 194 will return the piston assemblies to the position shown in FIG. 4 with the poppet adjacent ambient conduit 144 remaining open due to the higher ambient pressure, and the poppet adjacent conduit 142 being sealed against its seat.

The fourth condition, where the pressure in the tank 16 is greater than ambient 12 and it is desired to transfer water from the tank to ambient, the pump 146 is manipulated to pressurize the circuit 148 thereby opening the poppet adjacent the ambient conduit 144, with the other poppet being opened by the pressure from tank 16. As above, when enough water has been transferred, the release 200 is activated thereby releasing the pressure in circuit 148 and closing the poppet adjacent the conduit 144.

As can be seen from the description above, a simple and efficient buoyancy control system has been provided for submersibles. The very simplicity of the system and its components contribute to the inherent reliability thereof. Also, the

elimination of many valves and other associated equipment make the transfer of water ballast a simple one step operation whether it be switching pump assembly 18 on to pump water through valve 20 against the pressure gradient or manipulating pump 146 to meter fluid through the valve with the pressure gradient.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. A buoyancy control system comprising:

a tank assembly;

a pump assembly for transferring water between the tank and ambient, said pump assembly including a pump inlet and a pump discharge;

a first valve having at least two spools to control flow between the pump and the tank, said first valve fluidly connected to said pump, to said tank and to ambient seawater surrounding said system so that a pressure gradient between said tank and ambient acts on one of said spools controlling the flow to the pump inlet and acts on another of said spools controlling the flow from said pump discharge; and

a valve assembly to control flow between the tank and ambient.

2. The system of claim 1 wherein the spools are shifted by the pressure gradient into position so that the pump will transfer water against the pressure gradient.

3. The system of claim 1 wherein the valve assembly includes a metering valve and a pressure source fluidly connected thereto to actuate the metering valve.

4. The system of claim 3 wherein the metering valve is fluidly connected between the tank and ambient.

5. A buoyancy control system comprising:

a tank assembly;

a pump assembly for transferring water between said tank and ambient against a higher pressure of a pressure gradient therebetween;

a first valve utilizing means automatically positioned by said pressure gradient to permit said pump to transfer water from said tank to ambient and from ambient to said tank, which water is transferred only against said higher pressure; and

a valve assembly connected to utilize said pressure gradient to permit water to be transferred from said tank to ambient and from ambient to said tank, which water is transferred from said higher pressure.

6. A buoyancy control system comprising:

a tank assembly including a reservoir of seawater and a gas ullage within said tank, said gas creating a pressure on said reservoir;

means connected to provide ambient seawater to said system;

a pump assembly having inlet and discharge means connected to move seawater between said tank and said ambient seawater;

.a first valve having at least two spools, said valve controlling flow between said pump and said tank, said valve fluidly being connected to said pump, said tank and ambient, said fluid connection providing a pressure gradient between said ambient seawater and said reservoir so that said pressure gradient acts on one of said spools controlling the flow of seawater to said pump inlet and on another of said spools controlling the flow from said pump discharge; and

a valve assembly to control flow between said tank and ambient. 

1. A buoyancy control system comprising: a tank assembly; a pump assembly for transferring water between the tank and ambient, said pump assembly including a pump inlet and a pump discharge; a first valve having at least two spools to control flow between the pump and the tank, said first valve fluidly connected to said pump, to said tank and to ambient seawater surrounding said system so that a pressure gradient between said tank and ambient acts on one of said spools controlling the flow to the pump inlet and acts on another of said spools controlling the flow from said pump discharge; and a valve assembly to control flow between the tank and ambient.
 2. The system of claim 1 wherein the spools are shifted by the pressure gradient into position so that the pump will transfer water against the pressure gradient.
 3. The system of claim 1 wherein the valve assembly includes a metering valve and a pressure source fluidly connected thereto to actuate the metering valve.
 4. The system of claim 3 wherein the metering valve is fluidly connected between the tank and ambient.
 5. A buoyancy control system comprising: a tank assembly; a pump assembly for transferring water between said tank and ambient against a higher pressure of a pressure gradient therebetween; a first valve utilizing means automatically positioned by said pressure gradient to permit said pump to transfer water from said tank to ambient and from ambient to said tank, which water is transferred only against said higher pressure; and a valve assembly connected to utilize said pressure gradient to permit water to be transferred from said tank to ambient and from ambient to said tank, which water is transferred from said higher pressure.
 6. A Buoyancy control system comprising: a tank assembly including a reservoir of seawater and a gas ullage within said tank, said gas creating a pressure on said reservoir; means connected to provide ambient seawater to said system; a pump assembly having inlet and discharge means connected to move seawater between said tank and said ambient seawater; a first valve having at least two spools, said valve controlling flow between said pump and said tank, said valve fluidly being connected to said pump, said tank and ambient, said fluid connection providing a pressure gradient between said ambient seawater and said reservoir so that said pressure gradient acts on one of said spools controlling the flow of seawater to said pump inlet and on another of said spools controlling the flow from said pump discharge; and a valve assembly to control flow between said tank and ambient. 